Tissue Processing Flashcards
People that produces tissue sections of clear and adequate interpretations of microscopic structures and cellular changes
histotechnologist
the tissue from _______ to the state where it is completely infiltrated and a suitable histological wax, can be embedded and ready for section cutting
Fixation
Preserves tissues preventing autolysis or putrefaction
Fixation
Done ASAP after removal of the tissue
Fixation
Three objectives of Fixation
To preserve the tissue
To prevent breakdown of cellular elements
To coagulate or precipitate protoplasmic substances
Practical Considerations of Fixation
-Transfer the fixative in less than an hour
-10:1 fixative to specimen ration for excellent penetration
-Tissue must be small and thin (2-3 mm)
Prolonged Fixation
‘Shrinkage and hardening of tissue’, welcomes enzyme activity and immunological reactions
Most popular fixative
Formalin
Removal of calcium ions
Decalcification
Bones, teeth, calcified tumors, and calcified heart valves are in this process
Decalcification
involves slow substitution of the water in the tissues with an organic solvent
Dehydration
Recommended for dehydration
Ethyl Alcohol (Ethanol)
Fast-acting, mixes water and other solvents, penetrating tissues is easy
Ethanol
Cheap, rapid acting
Dehydrates in 1/2 to 2 hours
Acetone
Alcohol or a dehydration agent is removed than replaced with a substance that dissolves the wax
Clearing
Imparts optical clarity or transparency
“Change of appearance” indicates effectiveness/completeness of the process
Clearing
Removes an amount of fat from the tissues
Clearing
Most common clearing agent
1/2 to 1 hour
Xylene (Xylol)
Clearing agent is completely removed
Impregnation and Embedding
Allows easier handling and cutting very thin sections with no damage at all
Impregnation and Embedding
The tissue is placed into a precise arranged position
Embedding
Most important step in embedding
Correct Orientation
Embedding mediums
Paraffin Wax
Celloidin
Gelatin
Plastic
Peel away disposable embedding mold
Embedding Molds
Tissue is now trimmed into uniformly thin slices or “Sections”
Section Cutting (Microtomy)
Tissue components are made visible through dye and the like
Staining
Gives color and uses alcoholic dye solutions (ONE dye is used)
Direct Staining
Adds a mordant that serves as a link/bridge to make reactions possible
Indirect staining
Merely accelerates the reaction
Accentuator
Applied in specific period of time or desired intensity
Progressive Staining
Tissue is overstained and excess stain is removed
Regressive Staining
The ribbons are taken from the microtome and transferred to the warm water bath
Mounting
